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Boilerplate error? == No 'Intended status' indicated for this document; assuming Proposed Standard Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** The document seems to lack a both a reference to RFC 2119 and the recommended RFC 2119 boilerplate, even if it appears to use RFC 2119 keywords. RFC 2119 keyword, line 69: '...Discovery option SHOULD be included in...' RFC 2119 keyword, line 111: '...t Router Advertisement messages SHOULD...' RFC 2119 keyword, line 115: '...options MUST only use the prefixes fro...' RFC 2119 keyword, line 119: '...he SSM Range Discovery option MUST not...' RFC 2119 keyword, line 123: '...-local multicast range 224.0.0/24 MUST...' (1 more instance...) Miscellaneous warnings: ---------------------------------------------------------------------------- == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: The SSM range specified by routers originating Multicast Router Advertisement messages with the SSM Range Discovery option MUST not include any part of the link-local multicast range 224.0.0/24. Systems with a multicast capable IP host stack that receive a Multicast Router Advertisement message with a SSM Range Discovery option that includes destination addresses in the link-local multicast range 224.0.0/24 MUST use as the active SSM range the contents of the option excluding any addresses in the range 224.0.0/24. -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (17 June 2003) is 7611 days in the past. Is this intentional? 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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Internet Engineering Task Force MAGMA WG 2 INTERNET-DRAFT Isidor Kouvelas/Cisco 3 draft-ietf-magma-mrdssm-03.txt 17 June 2003 4 Expires: December 2003 6 Multicast Router Discovery SSM Range Option 8 Status of this Document 10 This document is an Internet-Draft and is in full conformance with all 11 provisions of Section 10 of RFC2026. 13 Internet-Drafts are working documents of the Internet Engineering Task 14 Force (IETF), its areas, and its working groups. Note that other groups 15 may also distribute working documents as Internet-Drafts. 17 Internet-Drafts are draft documents valid for a maximum of six months 18 and may be updated, replaced, or obsoleted by other documents at any 19 time. It is inappropriate to use Internet- Drafts as reference material 20 or to cite them other than as "work in progress." 22 The list of current Internet-Drafts can be accessed at 23 http://www.ietf.org/ietf/1id-abstracts.txt 25 The list of Internet-Draft Shadow Directories can be accessed at 26 http://www.ietf.org/shadow.html. 28 This document is a product of the IETF MAGMA WG. Comments should be 29 addressed to the authors, or the WG's mailing list at magma@ietf.org. 31 Abstract 33 This document defines the Multicast Router Discovery protocol 34 option for advertising the configured IPv4 Source Specific 35 Multicast destination address range. 37 1. Introduction 39 With current multicast deployment in the Internet, different 40 multicast routing protocols coexist and operate under separate parts of 41 the multicast address space [1]. Multicast routers are consistently 42 configured with information that maps specific multicast destination 43 address ranges to multicast routing protocols. Part of this 44 configuration describes the subset of the address space that is used by 45 source-specific multicast (SSM) [3]. Under current deployment, the 46 ability to extend the IPv4 SSM destination address range is used to 47 define SSM destination addresses that operate within administratively 48 scoped boundaries. Note that the SSM range for IPv6 is well defined for 49 all valid scopes [4] and a mechanism to allow additional ranges to 50 operate in SSM mode on a per-link bases is not required. 52 There are currently two requirements for a router to advertise its 53 configured SSM range on its attached links: 55 o On links with multiple multicast routers, advertisement of the 56 configured SSM range by each router can be used to discover 57 misconfigurations. 59 o IP systems with multicast sources or receivers can use the 60 advertisements to learn the SSM group range with which the network is 61 configured. 63 This document defines an optional extension for the IPv4 Multicast 64 Router Discovery protocol [2] that can be used by a router to advertise 65 the configured SSM address range. 67 2. SSM Range Discovery Option Format 69 The SSM Range Discovery option SHOULD be included in all Multicast 70 Router Advertisement messages [2]. It contains the list of multicast 71 destination address ranges that are configured to operate under Source 72 Specific Multicast on this router. The format of the option is as 73 follows: 75 0 1 2 3 76 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 77 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 78 | Type=X | Length=var | Mask-Len-1 | Prefix-1 ... 79 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 80 | Mask-Len-2 | Prefix-2 ... 81 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 82 | ... | 84 Type The type value of the Multicast Router Advertisement SSM Range 85 Discovery option is X (TBD by IANA). 87 Length 88 The length of the option in octets excluding the type and length 89 fields. The length of the SSM Range Discovery option is variable 90 and depends on the number of destination ranges present in the 91 option as well as the sizes of the ranges. 93 Mask-Len-n 94 The mask length in bits for the nth address range. 96 Prefix-n 97 The multicast destination address prefix for the nth range present 98 in this option. The size of the prefix field is variable and 99 depends on the number of significant bits in the prefix (specified 100 in the corresponding Mask-Len field). The field is padded by enough 101 trailing bits to make the end of the field fall on an octet 102 boundary. The value of the trailing bits must be sent as zero and 103 ignored on receipt. For example a prefix with a mask length field 104 holding the value 16 would have a prefix field that takes up two 105 octets and requires no padding. A prefix with a mask length of 17 106 would have a prefix field that takes up three octets and includes 7 107 trailing padding bits. 109 3. Notes on Option Processing 111 Routers originating Multicast Router Advertisement messages SHOULD 112 NOT include more than one SSM Range Discovery option in each message. 113 Systems with a multicast capable IP host stack that receive a Multicast 114 Router Advertisement message with more than one SSM Range Discovery 115 options MUST only use the prefixes from the last SSM Range Discovery 116 option in the message as the active SSM range. 118 The SSM range specified by routers originating Multicast Router 119 Advertisement messages with the SSM Range Discovery option MUST not 120 include any part of the link-local multicast range 224.0.0/24. Systems 121 with a multicast capable IP host stack that receive a Multicast Router 122 Advertisement message with a SSM Range Discovery option that includes 123 destination addresses in the link-local multicast range 224.0.0/24 MUST 124 use as the active SSM range the contents of the option excluding any 125 addresses in the range 224.0.0/24. 127 A router receiving a Multicast Router Advertisement message with an 128 SSM Range Discovery option MUST compare the contents of the option with 129 the multicast address ranges in the local SSM configuration and signal 130 any differences to the administrator in a rate-limited manner. 131 Signaling of range differences may be accomplished by a mechanism as 132 simple as an entry in the router log containing the address of the 133 router with the mismatch in configuration. 135 4. Security Considerations 137 Multicast Router Advertisement messages are IGMP messages sent to 138 the All-Systems multicast group (224.0.0.1) which is not forwarded by 139 routers. Only rogue systems on a connected link can masquerade as 140 multicast routers. Such rogue systems can include the SSM Range 141 Discovery option in their messages and cause the SSM range mapping to be 142 incorrectly set by hosts on the link. The next Multicast Router 143 Advertisement from a real valid router on the link will restore the 144 correct mapping. This spec mandates that routers log the reception of 145 inconsistent range advertisements which makes it easier to detect rogue 146 systems. 148 5. IANA Considerations 150 This document introduces the new SSM Range Discovery option for the 151 Multicast Router Discovery protocol. This option requires a new MRD type 152 value to be assigned by IANA. 154 6. Acknowledgments 156 The author would like to thank Bill Fenner and Dave Thaler for their 157 contribution to this document. 159 7. Authors' Addresses 161 Isidor Kouvelas 162 Cisco Systems 163 170 W. Tasman Drive 164 San Jose, CA 95134 165 kouvelas@cisco.com 167 8. Normative References 169 [1] Z. Albanna, K. Almeroth, D. Meyer, M. Schipper, "IANA Guidelines for 170 IPv4 Multicast Address Assignments", RFC 3171 (BCP 51), August 171 2001. 173 [2] S. Biswas, B. Haberman, "IGMP Multicast Router Discovery", Work In 174 Progress, , 2002. 176 9. Informative References 178 [3] H. Holbrook, B. Cain, "Source-Specific Multicast for IP", work in 179 progress, , 21 November 2001. 181 [4] B. Haberman, D. Thaler, "Unicast-Prefix-based IPv6 Multicast 182 Addresses", RFC 3306, August 2002.